Druggable regulators of nitric oxide production as new Alzheimer's disease therapeutics Summary: Nitrosative stress is a critical mediator of the onset and progression of Alzheimer's disease (AD): it precedes and is associated with neuritic dystrophy and dendritic spine loss, A/amyloid accumulation and deposition, cholinergic denervation and a memory loss phenotype in animal models of disease. Normally, nitric oxide (NO) is an important signaling molecule and the enzyme that produces it, nitric oxide synthase (NOS), regulates ApoE and its other protein partners via nitrosylation. Under pro-inflammatory conditions (e.g. AD), oxidative stress upregulates NOS. Excess NO combines with oxygen radicals forming the reactive nitrosylating species peroxynitrite, which in turn causes promiscuous dysregulation and indiscriminate damage. Because direct inhibition of NOS results in systemic toxicity, our unique strategy is to selectively reduce NO activity at sites of inflammation. This will be achieved by targeting Sigma- 1 receptors (S1R), because they become important regulators of NOS activity only under conditions of oxidative stress. Our hypothesis is that elevated brain NO levels can be lowered at inflammatory sites by drugs that promote S1R-mediated reductions in NOS activity. The path for discovery and proof-of-concept phases includes: A) synthesis of additional novel candidate molecules to impart the appropriate selectivity and drug-like characteristics to compounds that reduce NO levels and promote neuronal and/or glial cell survival in vitro under conditions of nitrosative stress; B) evaluate 1- of these leads in a transgenic mouse model of AD by measuring reductions in CNS A/amyloid burden, 3-nitrotyrosine levels and improvements in cognition. Novel high affinity S1R candidates (hits) have been identified in our preliminary work and now we seek to create leads with refined drug-like properties for testing our target and mechanism- based hypothesis for therapeutics designed to slow the progression of AD.